I have two favorite poetic forms: Free Verse and Blank Verse.
Free verse allows me to express myself effectively because of the 'freedom' to use whatever literary devices I desire.
However, I also find Blank Verse allows me to express myself effectively because of the constraints it imposes on me. I agree with the above post - I also enjoy the challenge of creating according to a prescribed pattern - in the case of Blank Verse, Iambic Pentameter.
It depends on the poem's topic and my frame of mind at the time of writing the original draft. Sometimes I need the free-for-all recipe that Free Verse lays out. Sometimes I need the structure and formality of Blank Verse to harness my thoughts into a cohesive story.